Wash, trim, and peel the beets, and slice them thinly. Reserve the beet greens. Arrange a layer of beet greens in a steamer and top with the sliced beets. Use the beet greens to keep each beet variety separate so the colors do not run. Prepare the vinaigrette by mixing the olive oil, balsamic vinegar, salt and pepper in a small mixing bowl. Set aside. Steam the beets until you can pierce them easily with a fork. Remove them from the steamer to small bowls, keeping each variety separate. Sprinkle half the vinaigrette over the beets. Cool to room temperature, and then refrigerate to chill thoroughly. To serve, line a chilled salad plate with the mizuna greens, arrange the steamed, marinated beets on the greens, top with a couple of slices of chevre, and garnish with the chopped filberts. Drizzle the remaining vinaigrette over salad just before serving.